Various host computers (and most personal computers) include an Advanced Technology Attachment (ATA) controller for communicating with ATA devices using an ATA bus. The controller typically has two channels, each of which is connected to an ATA bus, and each ATA bus can be connected to two devices. The host computer can include additional controllers to connect to more devices. However, additional controllers add cost, do not allow for command overlapping between devices and do not improve performance. Furthermore, appropriate cabling is difficult.
Alternative bus protocols are available. For instance, the small computer system interface (SCSI) allows 255 SCSI devices to be connected to a single SCSI bus. However, SCSI devices are expensive, and the SCSI controller is not normally provided in a personal computer. Furthermore, although SCSI improves performance over ATA, the SCSI data rate cannot be fully exploited by most host computers and SCSI devices.
Accordingly, it would be advantageous to increase the number of devices that can be connected to a single ATA bus.